Zaniolo was allowed to leave Italy's squad before their Euro 2024 qualifiers with Malta and England, along with fellow midfielder Sandro Tonali, after the players were told of their involvement in an investigation by Turin prosecutors.
"Aston Villa can confirm Nicolo Zaniolo is assisting the Italian Football Federation (FIGC) and the relevant authorities' investigation into alleged illegal betting activity," the Midlands club said in a statement.
"Zaniolo is training as normal with the first-team squad and available for selection ahead of this week's match with West Ham United."
The club said they will make no further comment during the ongoing process.
Newcastle United's Tonali is also available for their game at home to Crystal Palace on Saturday.
Aston Villa, who are in fifth place, four points behind leaders Tottenham Hotspur, host West Ham on Sunday.
